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Cerium - Praseodymium - Neodymium
Name, Symbol, NumberPraseodymium, Pr, 59
Chemical series Transition metals
Group, Period, Block_ [?], 6 , f
Density, Hardness 6640 kg/m3, no data
Appearance silvery white, yellowish tinge
Atomic Properties
Atomic weight 140.90765(2) amu
Atomic radius (calc.) 185 (247) pm
Covalent radius 165 pm
van der Waals radius no data
Electron configuration [Xe]6s24f3
e- 's per energy level2, 8, 18, 21, 8, 2
Oxidation states (Oxide) 3 (mildly basic)
Crystal structure hexagonal
Physical Properties
State of matter solid
Melting point 1204 K (1707.8 F)
Boiling point 3793 K (6368 F)
Molar volume 20.8 ×10-3 m3/mol
Heat of vaporization 296.8 kJ/mol
Heat of fusion 6.89 kJ/mol
Vapor pressure 1,333224E-06 Pa at 1070 K
Velocity of sound 2280 m/s at 293.15 K
Electronegativity 1.13 (Pauling scale)
Specific heat capacity 193 J/(kg*K)
Electrical conductivity 1.48 106/m ohm
Thermal conductivity 12.5 W/(m*K)
1st ionization potential 527 kJ/mol
2nd ionization potential 1020 kJ/mol
3rd ionization potential 2086 kJ/mol
4th ionization potential 3761 kJ/mol
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
141Pr100%141Pr is stable with 82 neutrons
142Pr{syn.}19.12 hβ-2.162 MeV142Nd
ε0.745 MeV142Ce
143Pr{syn.}13.57 dβ-0.934 MeV143Nd
SI units & STP are used except where noted.
Praseodymium is a chemical element in the periodic table that has the symbol Pr and atomic number 59.

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Notable Characteristics

Praseodymium is a soft silvery metallic element, and belongs to the lanthanide group. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation. For this reason, praseodymium should be stored under a light mineral oil or sealed in plastic or glass.


Uses of praseodymium:


The name Praseodymium comes from the Greek prasios, meaning green, and didymos, or twin.

In 1841, Mosander extracted the rare earth didymium[?] from lanthana. In 1874, Per Teodor Cleve[?] concluded that didymium was in fact two elements, and in 1879, Lecoq de Boisbaudran[?] isolated a new earth, Samarium, from didymium obtained from the mineral samarskite[?]. In 1885, the Austrian chemist baron C. F. Auer von Welsbach[?] separated didymium into two elements, Praseodymium and Neodymium, which gave salts of different colors.

Biological Role

Praseodymium has no known biological role.


Praseodymium is found in the rare earth minerals monazite and bastnasite, and can be recovered from bastnasite or monazite by an ion-exchange process[?]. Praseodymium also makes up about 5% of Misch metal.


Praseodymium compounds include:


Naturally occurring praseodymium is composed of one stable isotope, 141-Pr. 38 radioisotopes have been characterized with the most stable being 143-Pr with a half-life of 13.57 days and 142-Pr with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lifes that are less than 5.985 hours and the majority of these have half lifes that are less than 33 seconds. This element also has 6 meta states with the most stable being 138m-Pr (t 2.12 hours), 142m-Pr (t 14.6 minutes) and 134m-Pr (t 11 minutes).

The isotopes of praseodynium range in atomic weight from 120.955 amu (121-Pr) to 158.955 amu (159-Pr). The primary decay mode before the stable isotope, 141-Pr, is electron capture and the primary mode after is beta minus decay. The primary decay products before 141-Pr are element 58 (Cerium) isotopes and the primary products after are element 60 (Neodymium) isotopes.


Like all rare earths, praseodymium is of low to moderate toxicity.

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